Influence of 1523 K annealing on phase and magnetic properties in (Gd₁ − xEr_x)₅Si₂Ge₂ compounds

摘要

The (Gd_{1 − x} Er _x )₅Si₂Ge₂ (x = 0, 0·05, 0·1, 0·15 and 0·2) compounds were prepared from the high purity Gd metal (3 N) by arc melting, and then annealed at 1523 K (3 h). The phase, microstructure, Curie temperatures, magnetic hysteresis loss, and magnetocaloric effects were investigated. All samples retain the monoclinic Gd₅Si₂Ge₂ type structure. The temperature of magnetic transition decreases linearly from 281 K to 177 K with the increase of Er content from x = 0–0·2. Because the (Gd_{1 − x} Er _x )₅Si₂Ge₂ compounds keep the typical first-order structural/magnetic transition, they display large magnetic entropy near their magnetic transition temperatures. The maximum magnetic entropy change of (Gd_{1 − x} Er _x )Si₂Ge₂ compounds in the low magnetic field of 0~2·0 T are 15·5, 16·1, 15·3 and 15·2 J/kg K for x = 0·05, 0·1, 0·15 and 0·2, respectively.